speedometer accuracy

My truck, tracking by GPS, has always been exactly 3MPH fast on the speedometer. I think like someone said, less than 20MPH it is accurate.

No percentage points or anything, always 3MPH fast.

 

Speedometer - 60 mph ... GPS - 58 mph.

 

not exactly, the faster you go the greater the difference between speedo and gps speeds. Seems linear though, at 100 km/h its off by 3-4, at 200km/h its off by 7-9.

 

correct, if the tires are worn,or if the speedo accuracy is off, as you go faster the inaccuracy increases, thats why you dont see it as much at 25mph then at 75mph...

 

Just get a Scan Gauge and then you know you'll always be accurate lol.

 

From what I observed yesterday on my 245/75-16 AT20s:
-cruise at 72 mph on the speedometer
-GPS on phone read 71 mph. Garmin GPS read 72 mph.
-Ultragauge read 69-70 mph
-30 mile markers gave exactly 29 miles on the tripmeter

I bet there's a minor difference from the stock 30 psi to the 40+ in mine.

 

Scangauge and the speedo get their information from the same source.

GPS is the only thing that is accurate (usually).

 

A BIG "usually"

The Garmin Nuvi 660 that I ran before I got the Rosen shows a max speed of 667mph. I'll reset trip data but not "max"

I had that happen with previous Garmin units too. While I can't download track information from the 660, I was able to see what was happening in an older unit... it showed basically a change of 500ft with only microseconds between the data points.
More modern units appear to average 3 or more data points when coming up with their "max" display... my Zumo and wife's newer Nuvi display "realistic" max speeds.

 

Where in alberta do we have speed limits of 130?!

Anywho, why all this curfufle about the speedometer. We should start a lawsuit against for toyota for making us think we are going faster than we actually are!!!

 

Our 07 Jeep Liberty was 7-8% too fast. That is a problem because we are racking up mileage we are not even driving! We put on bigger tires and got it to within 2%.
The tacoma was off by 3% stock, new tires helped.

 

Is there a thread confirming this? How do you know? The reason I ask, you'll likely alraeady realize this, is because if the speedo and ODO both use hub spin as a metering device, then unless the flaw or inconsistancy is in the back of the speedo and not at the hub, both the ODO and speedo will be off.

 

Digital - Analog conversion.

And do you really think Toyota wants a lawsuit over a few miles?

 

So you're saying they're deliberating converting the speedo inaccurately?

lawsuit what?

 

No, I'm saying that there might be some inconsistency of speed due to timings and such. This also protects them from people saying the speedometer is making them speed as said before. The inaccuracy also falls within the regulations for vehicles.

The speedometer being analog and the ODO being digital could also have some discrepancies because it is trying to relay info in "realtime".

And lawsuits with racking up more than actual miles driven or going to fast causing speeding tickets vs going to slow.

 

You need to verify using mile markers or a GPS. Just because the speedo is off doesn't mean the odometer is off.

Very typical for Japanese motorcycles for the speedo to be as much as 10% fast, but the odometer is roughly half that.
It's not that big of a deal on motorcycles because the warranty is strictly time and not time/miles, and a 5-10% error will not impact resale value (of a motorcycle or a car)

In the case of my Taco, the speedo seems to be a consistent 3mph high no matter what my speed. I haven't checked it at the extremes, but compared to a GPS, it's been about 3mph fast at speeds between 55 and 80.

This flies in the face of "logic" because normally, the error would be a percentage, and 3mph off at 50 would be 4.5 off at 75, and 6 off at 100... the only possibility is that the needle was placed incorrectly on the spindle.
My speed is 3mph off, but on a recent trip to Austin, I compared my odo to mile markers and my GPS over 70+ miles and I was only a couple of 10ths off, so my odometer error was less than 0.5%.

+1

Honda got spanked in a civil case a few years ago and was forced to extend the warranties of the class action suit parties.

Yes.

Not so much North America, but in Europe, there are harsh penalties if a speedometer reads slower than actual speed.

 

The best way to check the ODO accuracy is to use the GPS (preferably over a long distance), same as checking the speed.
With all the different types and sizes of tires it would be almost impossible for any manufacturer to be dead on. They would rather be a little conservative from a legal standpoint.

 

use mile markers and the GPS versus the odometer and speedometer. safely, stop at a mile marker, reset the trip meter, and proceed at least 10 miles....those markers are surveyed so they are within inches of being accurate. the 10 mile trip will give a better understanding of how far off you are. get a STRAIGHT section of road if possible as you turn the differential will skew the miles SLIGHTLY, as one tire will turn more then the other and vice versa...adding to the distance traveled. also if you can set the cruise at 60mph and reset the tripmeter at the same time and TIME the distance to 10 miles. it should be 10 minutes exactly. there are many ways to determine the accuracy of the speedometer and odometer. i can tell you with my 2010 2wd ITS OFF, the MILES AND SPEED. a good 3%. im burning up my warranty that much faster but im going with bigger tires to offset it that 3% or close to it...think it adds 2.6% with 215 75 15s...just you should all try it that are saying the speedometer is inaccurate but the odometer is accurate...one should use the other signal to determine pulse to spin the speedo and odometer making them a symbiotic relationship

 

Damn, you guys are good. Thanks for all the replies.

 

3%

That's 3 miles every 100.
That's 3000 miles every 100,000.

So your 3/36 will instead run out at 3/35.

Not something I'd lose any sleep over